It is known that anhydrous magnesium dichloride derivatives which are suitable for the preparation of Ziegler-Natta catalysts can be obtained by reacting an organo magnesium or a Grignard reagent with a halogenated compound. For example, U.S. Pat. No. 4,186,107, and its equivalent FR-A-2464965, each describe the synthesis of a catalyst composed of a titanium halide deposited on a magnesium halide support. The support may be prepared by reacting a dialkyl magnesium with an alkyl aluminium halide in a hydrocarbon solvent. The support may be treated with an electron donor such as a dialkyl ether in order to provide a means for controlling its morphology. Very low temperatures are preferred in the synthesis of the catalyst and all the examples were conducted at around -65.degree. C. This presents a serious disadvantage in the industrial applicability of this method.
EP-A-98196 reports the synthesis of magnesium dichloride catalyst supports having spherical particles of controllable size distribution by reacting a dialkyl magnesium with an alkyl chloride in the presence of an electron donor, preferably an ether.
EP-A-68200 describes a process for the production of granular ethylene polymers having a large, uniform particle size and a high bulk density. An organic magnesium compound is reacted with a hydropolysiloxane or a silicon compound to give a silicon-containing reaction product which is then reacted with the reaction product of an organic aluminium chloride compound with a mixture of alcohols. The product of this reaction is further reacted with a halogen-containing titanium or vanadium compound. This approach is further developed in U.S. Pat. No. 4,223,118 which also requires the use of the reaction product of an organic magnesium compound with a hydropolysiloxane or silicon compound. This silicon-containing reaction product is further reacted with an aluminium alkoxide which optionally contains a halogen atom. These processes suffer from a disadvantage that complex synthetic procedures are required to achieve the desired catalyst.
EP-A-093454 reports a solid catalyst component for alpha-olefin polymerisation made by reacting a magnesium compound such as n-butyl, sec-butyl-magnesium with a catalyst such as obtained by reacting aluminium chloride with ethyl benzoate. No steps are taken to control the morphology or particle size distribution of the solid catalyst component.
U.S. Pat. No. 4,873,300 reports a catalyst preparation by reacting with a reducing halide source a mixture of a hydrocarbon soluble magnesium alkyl compound, an aliphatic alcohol and a titanium compound.